FreeBSD/Linux Kernel Cross Reference
sys/sys/mbuf.h

     /*
      * Copyright (c) 2004 The DragonFly Project.  All rights reserved.
      *
      * Copyright (c) 1982, 1986, 1988, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)mbuf.h      8.5 (Berkeley) 2/19/95
     * $FreeBSD: src/sys/sys/mbuf.h,v 1.44.2.17 2003/04/15 06:15:02 silby Exp $
     * $DragonFly: src/sys/sys/mbuf.h,v 1.54 2008/10/19 08:39:55 sephe Exp $
     */
    
    #ifndef _SYS_MBUF_H_
    #define _SYS_MBUF_H_
    
    #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
    
    #ifndef _SYS_TYPES_H_
    #include <sys/types.h>
    #endif
    #ifndef _SYS_PARAM_H_
    #include <sys/param.h>
    #endif
    #ifndef _SYS_QUEUE_H_
    #include <sys/queue.h>
    #endif
    #ifndef _NET_NETISR_H_
    #include <net/netisr.h>
    #endif
    #ifndef _NET_ETHERNET_H_
    #include <net/ethernet.h>
    #endif
    
    /*
     * Mbufs are of a single size, MSIZE (machine/param.h), which
     * includes overhead.  An mbuf may add a single "mbuf cluster" of size
     * MCLBYTES (also in machine/param.h), which has no additional overhead
     * and is used instead of the internal data area; this is done when
     * at least MINCLSIZE of data must be stored.
     */
    #define MLEN            (MSIZE - sizeof(struct m_hdr))  /* normal data len */
    #define MHLEN           (MLEN - sizeof(struct pkthdr))  /* data len w/pkthdr */
    #define MINCLSIZE       (MHLEN + 1)     /* smallest amount to put in cluster */
    #define M_MAXCOMPRESS   (MHLEN / 2)     /* max amount to copy for compression */
    
    /*
     * Macros for type conversion:
     * mtod(m, t)           -- Convert mbuf pointer to data pointer of correct type.
     * mtodoff(m, t, off)   -- Convert mbuf pointer at the specified offset to data
     *                         pointer of correct type.
     */
    #define mtod(m, t)              ((t)((m)->m_data))
    #define mtodoff(m, t, off)      ((t)((m)->m_data + (off)))
    
    /*
     * Header present at the beginning of every mbuf.
     */
    struct m_hdr {
            struct  mbuf *mh_next;          /* next buffer in chain */
            struct  mbuf *mh_nextpkt;       /* next chain in queue/record */
            caddr_t mh_data;                /* location of data */
            int     mh_len;                 /* amount of data in this mbuf */
            int     mh_flags;               /* flags; see below */
            short   mh_type;                /* type of data in this mbuf */
            short   mh_pad;                 /* padding */
            /* XXX implicit 4 bytes padding on x86_64 */
    #ifdef MBUF_DEBUG
            const char *mh_lastfunc;
    #endif
            union {
                    struct netmsg_packet mhm_pkt;   /* hardware->proto stack msg */
                    struct netmsg_pru_send mhm_snd; /* usrspace->proto stack msg */
                   struct netmsg_inarp mhm_arp;    /* proto stack<->route msg */
           } mh_msgu;
   };
   #define mh_netmsg       mh_msgu.mhm_pkt
   #define mh_sndmsg       mh_msgu.mhm_snd
   #define mh_arpmsg       mh_msgu.mhm_arp
   
   /* pf stuff */
   struct pkthdr_pf {
           void            *hdr;           /* saved hdr pos in mbuf, for ECN */
           void            *statekey;      /* pf stackside statekey */
           u_int           rtableid;       /* alternate routing table id */
           uint32_t        qid;            /* queue id */
           uint16_t        tag;            /* tag id */
           uint8_t         flags;
           uint8_t         routed;
           uint32_t        state_hash;     /* identifies 'connections' */
           uint8_t         ecn_af;         /* for altq_red */
           uint8_t         unused01;
           uint8_t         unused02;
           uint8_t         unused03;
           /* XXX implicit 4 bytes padding on x86_64 */
   };
   
   /* pkthdr_pf.flags */
   #define PF_TAG_GENERATED                0x01
   #define PF_TAG_FRAGCACHE                0x02
   #define PF_TAG_TRANSLATE_LOCALHOST      0x04
   #define PF_TAG_DIVERTED                 0x08
   #define PF_TAG_DIVERTED_PACKET          0x10
   #define PF_TAG_REROUTE                  0x20
   
   /*
    * Packet tag structure (see below for details).
    */
   struct m_tag {
           SLIST_ENTRY(m_tag)      m_tag_link;     /* List of packet tags */
           uint16_t                m_tag_id;       /* Tag ID */
           uint16_t                m_tag_len;      /* Length of data */
           uint32_t                m_tag_cookie;   /* ABI/Module ID */
   };
   
   SLIST_HEAD(packet_tags, m_tag);
   
   /*
    * Record/packet header in first mbuf of chain; valid only if M_PKTHDR is set.
    *
    * Be careful: The fields have been carefully ordered to avoid hidden padding.
    *             Keep this in mind, when adding or removing fields!
    */
   struct pkthdr {
           struct  ifnet *rcvif;           /* rcv interface */
           struct packet_tags tags;        /* list of packet tags */
   
           /* variables for ip and tcp reassembly */
           void    *header;                /* pointer to packet header */
           int     len;                    /* total packet length */
   
           /* variables for hardware checksum */
           int     csum_flags;             /* flags regarding checksum */
           int     csum_data;              /* data field used by csum routines */
           uint16_t csum_iphlen;           /* IP header length */
                                           /* valid if CSUM IP|UDP|TCP|TSO */
           uint8_t csum_thlen;             /* TCP/UDP header length */
                                           /* valid if CSUM UDP|TCP|TSO */
           uint8_t csum_lhlen;             /* link header length */
   
           uint16_t tso_segsz;             /* TSO segment size */
           uint16_t ether_vlantag;         /* ethernet 802.1p+q vlan tag */
   
           uint16_t hash;                  /* packet hash */
           uint16_t unused1;               /* reserved for route table id */
           uint32_t unused2;               /* reserved for codel timestamp */
   
           uint16_t wlan_seqno;            /* IEEE 802.11 seq no. */
           /*
            * Valid if BRIDGE_MBUF_TAGGED is set in fw_flags, records
            * the original ether source address (if compatible).
            */
           uint8_t ether_br_shost[ETHER_ADDR_LEN];
   
           /* firewall flags */
           uint32_t fw_flags;              /* flags for FW */
   
           /* variables for PF processing */
           struct pkthdr_pf pf;            /* structure for PF */
   };
   
   /*
    * Description of external storage mapped into mbuf; valid only if M_EXT is set.
    */
   struct m_ext {
           caddr_t ext_buf;                /* start of buffer */
           void    (*ext_free)(void *);
           u_int   ext_size;               /* size of buffer, for ext_free */
           void    (*ext_ref)(void *);
           void    *ext_arg;
   };
   
   /*
    * The core of the mbuf object along with some shortcut defines for
    * practical purposes.
    */
   struct mbuf {
           struct  m_hdr m_hdr;
           union {
                   struct {
                           struct  pkthdr MH_pkthdr;       /* M_PKTHDR set */
                           union {
                                   struct  m_ext MH_ext;   /* M_EXT set */
                                   char    MH_databuf[MHLEN];
                           } MH_dat;
                   } MH;
                   char    M_databuf[MLEN];                /* !M_PKTHDR, !M_EXT */
           } M_dat;
   };
   #define m_next          m_hdr.mh_next
   #define m_len           m_hdr.mh_len
   #define m_data          m_hdr.mh_data
   #define m_type          m_hdr.mh_type
   #define m_flags         m_hdr.mh_flags
   #define m_nextpkt       m_hdr.mh_nextpkt
   #define m_pkthdr        M_dat.MH.MH_pkthdr
   #define m_ext           M_dat.MH.MH_dat.MH_ext
   #define m_pktdat        M_dat.MH.MH_dat.MH_databuf
   #define m_dat           M_dat.M_databuf
   
   /*
    * Code that uses m_act should be converted to use m_nextpkt
    * instead; m_act is historical and deprecated.
    */
   #define m_act           m_nextpkt
   
   /*
    * mbuf flags.
    */
   #define M_EXT           0x0001  /* has associated external storage */
   #define M_PKTHDR        0x0002  /* start of record */
   #define M_EOR           0x0004  /* end of record */
   #define M_PROTO1        0x0008  /* protocol-specific */
   #define M_PROTO2        0x0010  /* protocol-specific */
   #define M_PROTO3        0x0020  /* protocol-specific */
   #define M_PROTO4        0x0040  /* protocol-specific */
   #define M_PROTO5        0x0080  /* protocol-specific */
   
   /*
    * mbuf pkthdr flags (also stored in m_flags).
    */
   #define M_BCAST         0x0100  /* send/received as link-level broadcast */
   #define M_MCAST         0x0200  /* send/received as link-level multicast */
   #define M_FRAG          0x0400  /* packet is a fragment of a larger packet */
   #define M_FIRSTFRAG     0x0800  /* packet is first fragment */
   #define M_LASTFRAG      0x1000  /* packet is last fragment */
   #define M_CLCACHE       0x2000  /* mbuf allocated from the cluster cache */
   #define M_EXT_CLUSTER   0x4000  /* standard cluster else special */
   #define M_PHCACHE       0x8000  /* mbuf allocated from the pkt header cache */
   #define M_NOTIFICATION  0x10000 /* notification event */
   #define M_VLANTAG       0x20000 /* ether_vlantag is valid */
   #define M_MPLSLABELED   0x40000 /* packet is mpls labeled */
   #define M_LENCHECKED    0x80000 /* packet proto lengths are checked */
   #define M_HASH          0x100000/* hash field in pkthdr is valid */
   #define M_PROTO6        0x200000/* protocol-specific */
   #define M_PROTO7        0x400000/* protocol-specific */
   #define M_PROTO8        0x800000/* protocol-specific */
   #define M_CKHASH        0x1000000/* hash needs software verification */
   #define M_PRIO          0x2000000/* high priority mbuf */
   
   /*
    * Flags copied when copying m_pkthdr.
    */
   #define M_COPYFLAGS     (M_PKTHDR|M_EOR|M_PROTO1|M_PROTO2|M_PROTO3 | \
                            M_PROTO4|M_PROTO5|M_PROTO6|M_PROTO7|M_PROTO8 | \
                            M_BCAST|M_MCAST|M_FRAG|M_FIRSTFRAG|M_LASTFRAG | \
                            M_VLANTAG|M_MPLSLABELED | \
                            M_LENCHECKED|M_HASH|M_CKHASH|M_PRIO)
   
   /*
    * Flags indicating hw checksum support and sw checksum requirements.
    */
   #define CSUM_IP                 0x0001          /* will csum IP */
   #define CSUM_TCP                0x0002          /* will csum TCP */
   #define CSUM_UDP                0x0004          /* will csum UDP */
   #define CSUM_IP_FRAGS           0x0008          /* will csum IP fragments */
   #define CSUM_FRAGMENT           0x0010          /* will do IP fragmentation */
   
   #define CSUM_IP_CHECKED         0x0100          /* did csum IP */
   #define CSUM_IP_VALID           0x0200          /*   ... the csum is valid */
   #define CSUM_DATA_VALID         0x0400          /* csum_data field is valid */
   #define CSUM_PSEUDO_HDR         0x0800          /* csum_data has pseudo hdr */
   #define CSUM_FRAG_NOT_CHECKED   0x1000          /* did _not_ csum fragment
                                                    * NB: This flag is only used
                                                    * by IP defragmenter.
                                                    */
   #define CSUM_TSO                0x2000          /* will do TCP segmentation */
   
   #define CSUM_DELAY_DATA         (CSUM_TCP | CSUM_UDP)
   #define CSUM_DELAY_IP           (CSUM_IP)       /* XXX add ipv6 here too? */
   
   /*
    * Flags indicating PF processing status
    */
   #define FW_MBUF_GENERATED       0x00000001
   #define PF_MBUF_STRUCTURE       0x00000002      /* m_pkthdr.pf valid */
   #define PF_MBUF_ROUTED          0x00000004      /* pf_routed field is valid */
   #define PF_MBUF_TAGGED          0x00000008
   #define XX_MBUF_UNUSED10        0x00000010
   #define XX_MBUF_UNUSED20        0x00000020
   #define IPFORWARD_MBUF_TAGGED   0x00000040
   #define DUMMYNET_MBUF_TAGGED    0x00000080
   #define BRIDGE_MBUF_TAGGED      0x00000100
   #define FW_MBUF_REDISPATCH      0x00000200
   #define IPFW_MBUF_GENERATED     FW_MBUF_GENERATED
   /*
    * mbuf types.
    */
   #define MT_FREE         0       /* should be on free list */
   #define MT_DATA         1       /* dynamic (data) allocation */
   #define MT_HEADER       2       /* packet header */
   #define MT_SONAME       3       /* socket name */
   /* 4 was MT_TAG */
   #define MT_CONTROL      5       /* extra-data protocol message */
   #define MT_OOBDATA      6       /* expedited data  */
   #define MT_NTYPES       7       /* number of mbuf types for mbtypes[] */
   
   /*
    * General mbuf allocator statistics structure.
    *
    * NOTE: Make sure this struct's size is multiple cache line size.
    */
   struct mbstat {
           u_long  m_mbufs;        /* mbufs obtained from page pool */
           u_long  m_clusters;     /* clusters obtained from page pool */
           u_long  m_jclusters;    /* jclusters obtained from page pool */
           u_long  m_clfree;       /* free clusters */
           u_long  m_drops;        /* times failed to find space */
           u_long  m_wait;         /* times waited for space */
           u_long  m_drain;        /* times drained protocols for space */
           u_long  m_mcfail;       /* times m_copym failed */
           u_long  m_mpfail;       /* times m_pullup failed */
           u_long  m_msize;        /* length of an mbuf */
           u_long  m_mclbytes;     /* length of an mbuf cluster */
           u_long  m_mjumpagesize; /* length of a jumbo mbuf cluster */
           u_long  m_minclsize;    /* min length of data to allocate a cluster */
           u_long  m_mlen;         /* length of data in an mbuf */
           u_long  m_mhlen;        /* length of data in a header mbuf */
           u_long  m_pad;          /* pad to cache line size (64B) */
   };
   
   /*
    * Flags specifying how an allocation should be made.
    */
   
   #define MB_DONTWAIT     0x4
   #define MB_TRYWAIT      0x8
   #define MB_WAIT         MB_TRYWAIT
   
   /*
    * Mbuf to Malloc Flag Conversion.
    */
   #define MBTOM(how)      ((how) & MB_TRYWAIT ? M_WAITOK : M_NOWAIT)
   
   /*
    * These are identifying numbers passed to the m_mballoc_wait function,
    * allowing us to determine whether the call came from an MGETHDR or
    * an MGET.
    */
   #define MGETHDR_C      1
   #define MGET_C         2
   
   /*
    * mbuf allocation/deallocation macros (YYY deprecated, too big):
    *
    *      MGET(struct mbuf *m, int how, int type)
    * allocates an mbuf and initializes it to contain internal data.
    *
    *      MGETHDR(struct mbuf *m, int how, int type)
    * allocates an mbuf and initializes it to contain a packet header
    * and internal data.
    */
   #define MGET(m, how, type) do {                                         \
           (m) = m_get((how), (type));                                     \
   } while (0)
   
   #define MGETHDR(m, how, type) do {                                      \
           (m) = m_gethdr((how), (type));                                  \
   } while (0)
   
   /*
    * MCLGET adds such clusters to a normal mbuf.  The flag M_EXT is set upon
    * success.
    * Deprecated.  Use m_getcl() or m_getl() instead.
    */
   #define MCLGET(m, how) do {                                             \
           m_mclget((m), (how));                                           \
   } while (0)
   
   /*
    * NB: M_COPY_PKTHDR is deprecated; use either M_MOVE_PKTHDR
    *     or m_dup_pkthdr.
    */
   /*
    * Move mbuf pkthdr from "from" to "to".
    * from should have M_PKTHDR set, and to must be empty.
    * from no longer has a pkthdr after this operation.
    */
   #define M_MOVE_PKTHDR(_to, _from)       m_move_pkthdr((_to), (_from))
   
   /*
    * Set the m_data pointer of a newly-allocated mbuf (m_get/MGET) to place
    * an object of the specified size at the end of the mbuf, longword aligned.
    */
   #define M_ALIGN(m, len) do {                                            \
           (m)->m_data += (MLEN - (len)) & ~(sizeof(long) - 1);            \
   } while (0)
   
   /*
    * As above, for mbufs allocated with m_gethdr/MGETHDR
    * or initialized by M_COPY_PKTHDR.
    */
   #define MH_ALIGN(m, len) do {                                           \
           (m)->m_data += (MHLEN - (len)) & ~(sizeof(long) - 1);           \
   } while (0)
   
   /*
    * Check if we can write to an mbuf.
    */
   #define M_EXT_WRITABLE(m)       (m_sharecount(m) == 1)
   #define M_WRITABLE(m)           (!((m)->m_flags & M_EXT) || M_EXT_WRITABLE(m))
   
   /*
    * Check if the supplied mbuf has a packet header, or else panic.
    */
   #define M_ASSERTPKTHDR(m)                                               \
           KASSERT(m != NULL && m->m_flags & M_PKTHDR,                     \
                   ("%s: invalid mbuf or no mbuf packet header!", __func__))
   
   /*
    * Compute the amount of space available before the current start of data.
    * The M_EXT_WRITABLE() is a temporary, conservative safety measure: the burden
    * of checking writability of the mbuf data area rests solely with the caller.
    */
   #define M_LEADINGSPACE(m)                                               \
           ((m)->m_flags & M_EXT ?                                         \
               (M_EXT_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0): \
               (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :     \
               (m)->m_data - (m)->m_dat)
   
   /*
    * Compute the amount of space available after the end of data in an mbuf.
    * The M_WRITABLE() is a temporary, conservative safety measure: the burden
    * of checking writability of the mbuf data area rests solely with the caller.
    */
   #define M_TRAILINGSPACE(m)                                              \
           ((m)->m_flags & M_EXT ?                                         \
               (M_WRITABLE(m) ? (m)->m_ext.ext_buf + (m)->m_ext.ext_size   \
                   - ((m)->m_data + (m)->m_len) : 0) :                     \
               &(m)->m_dat[MLEN] - ((m)->m_data + (m)->m_len))
   
   /*
    * Arrange to prepend space of size plen to mbuf m.
    * If a new mbuf must be allocated, how specifies whether to wait.
    * If how is MB_DONTWAIT and allocation fails, the original mbuf chain
    * is freed and m is set to NULL.
    */
   #define M_PREPEND(m, plen, how) do {                                    \
           struct mbuf **_mmp = &(m);                                      \
           struct mbuf *_mm = *_mmp;                                       \
           int _mplen = (plen);                                            \
           int __mhow = (how);                                             \
                                                                           \
           if (M_LEADINGSPACE(_mm) >= _mplen) {                            \
                   _mm->m_data -= _mplen;                                  \
                   _mm->m_len += _mplen;                                   \
           } else                                                          \
                   _mm = m_prepend(_mm, _mplen, __mhow);                   \
           if (_mm != NULL && (_mm->m_flags & M_PKTHDR))                   \
                   _mm->m_pkthdr.len += _mplen;                            \
           *_mmp = _mm;                                                    \
   } while (0)
   
   /* Length to m_copy to copy all. */
   #define M_COPYALL       1000000000
   
   /* Compatibility with 4.3 */
   #define m_copy(m, o, l) m_copym((m), (o), (l), MB_DONTWAIT)
   
   #ifdef _KERNEL
   extern  u_int            m_clalloc_wid; /* mbuf cluster wait count */
   extern  u_int            m_mballoc_wid; /* mbuf wait count */
   extern  int              max_linkhdr;   /* largest link-level header */
   extern  int              max_protohdr;  /* largest protocol header */
   extern  int              max_hdr;       /* largest link+protocol header */
   extern  int              max_datalen;   /* MHLEN - max_hdr */
   extern  int              mbuf_wait;     /* mbuf sleep time */
   extern  int              nmbclusters;
   extern  int              nmbufs;
   
   struct uio;
   
   void             m_adj(struct mbuf *, int);
   void             m_align(struct mbuf *, int);
   int              m_apply(struct mbuf *, int, int,
                       int (*)(void *, void *, u_int), void *);
   int             m_append(struct mbuf *, int, c_caddr_t);
   void             m_cat(struct mbuf *, struct mbuf *);
   u_int            m_countm(struct mbuf *m, struct mbuf **lastm, u_int *mbcnt);
   void             m_copyback(struct mbuf *, int, int, caddr_t);
   void             m_copydata(const struct mbuf *, int, int, caddr_t);
   struct  mbuf    *m_copym(const struct mbuf *, int, int, int);
   struct  mbuf    *m_copypacket(struct mbuf *, int);
   struct  mbuf    *m_defrag(struct mbuf *, int);
   struct  mbuf    *m_defrag_nofree(struct mbuf *, int);
   struct  mbuf    *m_devget(char *, int, int, struct ifnet *,
                     void (*copy)(volatile const void *, volatile void *, size_t));
   struct  mbuf    *m_dup(struct mbuf *, int);
   struct  mbuf    *m_dup_data(struct mbuf *, int);
   int              m_dup_pkthdr(struct mbuf *, const struct mbuf *, int);
   void             m_extadd(struct mbuf *, caddr_t, u_int, void (*)(void *),
                     void (*)(void *), void *);
   #ifdef MBUF_DEBUG
   struct  mbuf    *_m_free(struct mbuf *, const char *name);
   void             _m_freem(struct mbuf *, const char *name);
   #else
   struct  mbuf    *m_free(struct mbuf *);
   void             m_freem(struct mbuf *);
   #endif
   struct  mbuf    *m_get(int, int);
   struct  mbuf    *m_getc(int len, int how, int type);
   struct  mbuf    *m_getcl(int how, short type, int flags);
   struct  mbuf    *m_getjcl(int how, short type, int flags, size_t size);
   struct  mbuf    *m_getclr(int, int);
   struct  mbuf    *m_gethdr(int, int);
   struct  mbuf    *m_getm(struct mbuf *, int, int, int);
   struct  mbuf    *m_getptr(struct mbuf *, int, int *);
   struct  mbuf    *m_last(struct mbuf *m);
   u_int            m_lengthm(struct mbuf *m, struct mbuf **lastm);
   void             m_move_pkthdr(struct mbuf *, struct mbuf *);
   struct  mbuf    *m_prepend(struct mbuf *, int, int);
   void             m_print(const struct mbuf *m);
   struct  mbuf    *m_pulldown(struct mbuf *, int, int, int *);
   struct  mbuf    *m_pullup(struct mbuf *, int);
   struct  mbuf    *m_split(struct mbuf *, int, int);
   struct  mbuf    *m_uiomove(struct uio *);
   struct  mbuf    *m_unshare(struct mbuf *, int);
   void            m_mclget(struct mbuf *m, int how);
   int             m_sharecount(struct mbuf *m);
   void            m_chtype(struct mbuf *m, int type);
   int             m_devpad(struct mbuf *m, int padto);
   
   #ifdef MBUF_DEBUG
   
   void            mbuftrackid(struct mbuf *, int);
   
   #define m_free(m)       _m_free(m, __func__)
   #define m_freem(m)      _m_freem(m, __func__)
   
   #else
   
   #define mbuftrackid(m, id)      /* empty */
   
   #endif
   
   /*
    * Allocate the right type of mbuf for the desired total length.
    * The mbuf returned does not necessarily cover the entire requested length.
    * This function follows mbuf chaining policy of allowing MINCLSIZE
    * amount of chained mbufs.
    */
   static __inline struct mbuf *
   m_getl(int len, int how, int type, int flags, int *psize)
   {
           struct mbuf *m;
           int size;
   
           if (len >= MINCLSIZE) {
                   m = m_getcl(how, type, flags);
                   size = MCLBYTES;
           } else if (flags & M_PKTHDR) {
                   m = m_gethdr(how, type);
                   size = MHLEN;
           } else {
                   m = m_get(how, type);
                   size = MLEN;
           }
           if (psize != NULL)
                   *psize = size;
           return (m);
   }
   
   static __inline struct mbuf *
   m_getlj(int len, int how, int type, int flags, int *psize)
   {
           if (len > MCLBYTES) {
                   struct mbuf *m;
   
                   m = m_getjcl(how, type, flags, MJUMPAGESIZE);
                   if (psize != NULL)
                           *psize = MJUMPAGESIZE;
                   return m;
           }
           return m_getl(len, how, type, flags, psize);
   }
   
   /*
    * Get a single mbuf that covers the requested number of bytes.
    * This function does not create mbuf chains.  It explicitly marks
    * places in the code that abuse mbufs for contiguous data buffers.
    */
   static __inline struct mbuf *
   m_getb(int len, int how, int type, int flags)
   {
           struct mbuf *m;
           int mbufsize = (flags & M_PKTHDR) ? MHLEN : MLEN;
   
           if (len > mbufsize)
                   m = m_getcl(how, type, flags);
           else if (flags & M_PKTHDR)
                   m = m_gethdr(how, type);
           else
                   m = m_get(how, type);
           return (m);
   }
   
   /*
    * Packets may have annotations attached by affixing a list
    * of "packet tags" to the pkthdr structure.  Packet tags are
    * dynamically allocated semi-opaque data structures that have
    * a fixed header (struct m_tag) that specifies the size of the
    * memory block and a <cookie,type> pair that identifies it.
    * The cookie is a 32-bit unique unsigned value used to identify
    * a module or ABI.  By convention this value is chose as the
    * date+time that the module is created, expressed as the number of
    * seconds since the epoch (e.g. using date -u +'%s').  The type value
    * is an ABI/module-specific value that identifies a particular annotation
    * and is private to the module.  For compatibility with systems
    * like openbsd that define packet tags w/o an ABI/module cookie,
    * the value PACKET_ABI_COMPAT is used to implement m_tag_get and
    * m_tag_find compatibility shim functions and several tag types are
    * defined below.  Users that do not require compatibility should use
    * a private cookie value so that packet tag-related definitions
    * can be maintained privately.
    *
    * Note that the packet tag returned by m_tag_alloc has the default
    * memory alignment implemented by kmalloc.  To reference private data
    * one can use a construct like:
    *
    *      struct m_tag *mtag = m_tag_alloc(...);
    *      struct foo *p = m_tag_data(mtag);
    *
    * if the alignment of struct m_tag is sufficient for referencing members
    * of struct foo.  Otherwise it is necessary to embed struct m_tag within
    * the private data structure to insure proper alignment; e.g.
    *
    *      struct foo {
    *              struct m_tag    tag;
    *              ...
    *      };
    *      struct foo *p = (struct foo *)m_tag_alloc(...);
    *      struct m_tag *mtag = &p->tag;
    */
   
   #define PACKET_TAG_NONE                         0  /* Nadda */
   
   /* Packet tag for use with PACKET_ABI_COMPAT */
   #define PACKET_TAG_IPSEC_IN_DONE                1  /* IPsec applied, in */
   /* struct tdb_indent */
   #define PACKET_TAG_IPSEC_OUT_DONE               2  /* IPsec applied, out */
   /* struct tdb_indent */
   #define PACKET_TAG_IPSEC_IN_CRYPTO_DONE         3  /* NIC IPsec crypto done */
   /* struct tdb_indent, never added */
   #define PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED      4  /* NIC IPsec crypto req'ed */
   /* struct tdb_indent, never added */
   #define PACKET_TAG_IPSEC_PENDING_TDB            5  /* Reminder to do IPsec */
   /* struct tdb_indent, never added */
   #define PACKET_TAG_ENCAP                        6 /* Encap.  processing */
   /* struct ifnet *, the GIF interface */
   #define PACKET_TAG_IPSEC_HISTORY                7 /* IPSEC history */
   /* struct ipsec_history */
   #define PACKET_TAG_IPV6_INPUT                   8 /* IPV6 input processing */
   /* struct ip6aux */
   #define PACKET_TAG_IPFW_DIVERT                  9 /* divert info */
   /* struct divert_info */
   #define PACKET_TAG_DUMMYNET                     15 /* dummynet info */
   /* struct dn_pkt */
   #define PACKET_TAG_IPFORWARD                    18 /* ipforward info */
   /* struct sockaddr_in */
   #define PACKET_TAG_IPSRCRT                      27 /* IP srcrt opts */
   /* struct ip_srcrt_opt */
   #define PACKET_TAG_CARP                         28 /* CARP info */
   /* struct pf_mtag */
   #define PACKET_TAG_PF                           29 /* PF info */
   
   #define PACKET_TAG_PF_DIVERT                    0x0200 /* pf(4) diverted packet */
           
   
   /* Packet tag routines */
   struct  m_tag   *m_tag_alloc(uint32_t, int, int, int);
   void             m_tag_free(struct m_tag *);
   void             m_tag_prepend(struct mbuf *, struct m_tag *);
   void             m_tag_unlink(struct mbuf *, struct m_tag *);
   void             m_tag_delete(struct mbuf *, struct m_tag *);
   void             m_tag_delete_chain(struct mbuf *);
   struct  m_tag   *m_tag_locate(struct mbuf *, uint32_t, int, struct m_tag *);
   struct  m_tag   *m_tag_copy(struct m_tag *, int);
   int              m_tag_copy_chain(struct mbuf *, const struct mbuf *, int);
   void             m_tag_init(struct mbuf *);
   struct  m_tag   *m_tag_first(struct mbuf *);
   struct  m_tag   *m_tag_next(struct mbuf *, struct m_tag *);
   
   /* these are for openbsd compatibility */
   #define MTAG_ABI_COMPAT         0               /* compatibility ABI */
   
   static __inline void *
   m_tag_data(struct m_tag *tag)
   {
           return ((void *)(tag + 1));
   }
   
   static __inline struct m_tag *
   m_tag_get(int type, int length, int wait)
   {
           return m_tag_alloc(MTAG_ABI_COMPAT, type, length, wait);
   }
   
   static __inline struct m_tag *
   m_tag_find(struct mbuf *m, int type, struct m_tag *start)
   {
           return m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
   }
   
   #endif  /* _KERNEL */
   
   #endif  /* _KERNEL || _KERNEL_STRUCTURES */
   #endif  /* !_SYS_MBUF_H_ */

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